Marine fouling organisms refer to the whole host of organisms that can attach to and grow on the hulls of boats and the surface of other submerged artificial structures.
There are more than 2000 reported biofoulers in the world, the most harmful ones of which include barnacles, oysters, mussels, tubeworms and bryozoans, etc. There are about 200 main biofoulers in Chinese coastal area. These fouling organisms can cause extensive damage to commercially-important marine structures, which is one of the most serious problems in maritime and aquaculture industries. They can increase frictional resistance on the hulls of ships, leading to consumption of more fuel to maintain a normal speed, cause marine machinery and instrument equipment failure, absorb the acoustic energy of sound waves and sequentially make acoustic instrument ineffective, accelerate the corrosion of the substrate (e.g., steel material, aluminum material etc.) surfaces, increase the cross-sectional area of stakes and columns of marine structures and hence the impact caused by waves and ocean currents, increase the weight of buoys, block seawater pipes, decrease water exchange through aquaculture net boxes, and other negative effects. It is estimated that governments and industry spend over US $6.5 billion annually to prevent and control marine biofouling.
The study of biofouling and antifouling technology has received widespread attention from different coastal countries and areas because of the importance in the military and economic area. Common strategies of preventing marine biofouling include chlorine release, electrolysis antifouling, ultrasound, impressed current, the use of radioactive material, submerged mechanical cleaning, coating marine antifouling paints and so on. Among these, coating antifouling paints is the most effective way because it is a mature technology using simple procedures and has broad application scope. However, it is crucial to discover suitable marine antifoulants in the development of marine antifouling paints. With the prohibited use of the toxic antifoulants such as organic arsenic compounds, organo-lead compounds, mercuric oxide, and dichlorodithenyltrichloroethane (DDT) after 1970s, organotins, represented by tributyltin (TBT), and cuprous oxide were effectively used to prevent marine biofouling as common anti-fouling agents. However, it has been discovered that TBT persists in water and sediments, killing marine organisms in addition to those attached to ship hulls since 1980s. High concentrations of TBT in shellfish on the coast of France caused the collapse of commercial shell fisheries in at least one area. TBT caused shell deformations in oysters and sex changes (imposex) in gastropod, and bioaccumulated in fish and mammals. These events and findings prompted the Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO) to implement a ban on the application of TBT paints from Jan. 1, 2003, with the intent that no TBT paints will remain on vessels after 2008. At present, antifouling paints containing copper and its compounds (e.g., cuprous oxide) have gained dominance in the market. However copper can accumulate in ocean, especially in harbour and hence cause massive death of marine algae which will impact the food web in the marine environment. Therefore finally copper and its compounds used as antifoulants will be replaced.
In order to protect the marine environment, biologists and natural product chemists have industriously been searching for effective and environmentally friendly natural antifoulants from natural resources. Natural products have no or very low acute and chronic toxicity to marine organisms, can be easily and quickly degraded and thus fail to cause permanent accumulation in the marine environment, and are abundantly available from natural resources. So far, a number of natural products with antifouling activities have been discovered from extracts of natural resources such as marine plants and animals and terrestrial plants, including terpenoids, alkynes, polycyclic compound, Steroids, isothiocyanates, etc. Most of these natural products have obvious repellent action to marine fouling organisms, but cause little or no damage to the marine environment. Therefore, it is hopeful to obtain non-toxic, high-efficient, broad-spectrum, degradable natural antifoulants and thus replace the toxic antifoulants.
The present invention provides a number of environmentally-friendly, natural anti-fouling agents, compositions, and applications.